Heat treatable coated glass pane

ABSTRACT

A coated glass pane comprising at least the following layers: a glass substrate and at least one absorbing layer based on at least one metal silicide and/or metal silicide nitride wherein the at least one absorbing layer is embedded between and contacts two layers based on an (oxi)nitride of Si and/or an (oxi)nitride of Al and/or alloys thereof.

BACKGROUND OF THE INVENTION

The invention relates to heat treatable coated glass panes with alow-emissivity (low-e) and/or solar control coating. The invention alsorelates to methods of manufacturing said panes.

Heat treated glass panes which are toughened to impart safety propertiesand/or are bent are required for a large number of areas of application,for example for architectural or motor vehicle glazings. It is knownthat for thermally toughening and/or bending glass panes it is necessaryto process the glass panes by a heat treatment at temperatures near orabove the softening point of the glass used and then either to toughenthem by rapid cooling or to bend them with the aid of bending means. Therelevant temperature range for standard float glass of the soda limesilica type is typically about 580-690° C., the glass panes being keptin this temperature range for several minutes before initiating theactual toughening and/or bending process.

“Heat treatment”, “heat treated” and “heat treatable” in the followingdescription and in the claims refer to thermal bending and/or tougheningprocesses such as mentioned before and to other thermal processes duringwhich a coated glass pane reaches temperatures in the range of about580-690° C. for a period of several minutes, e.g., for up to about 10minutes. A coated glass pane is deemed to be heat treatable if itsurvives a heat treatment without significant damage, typical damagescaused by heat treatments being high haze values, pinholes or spots.

The inventors of the present invention have found that the parameter“haze” usually referred to when characterising the heat treatability oflow-e and/or solar control coatings is often insufficient, as it doesnot fully reflect all types of defects that may arise during coating,heat treating, processing and/or handling of coated glass panes. Some ofthe known heat treatable coated glass panes show significant and clearlynoticeable modifications of their optical properties and particularly oftheir reflection colour during a heat treatment.

It is desirable to be able to manufacture a range of coated productswith a variety of light and/or heat transmission values in order to meetparticular needs. One approach to address this objective is to use acommon multilayer stack or platform for each of the different producttypes (e.g. low-e and solar control, and both toughenable andnon-toughenable products) and then tune the optical properties of thestack by adding different thicknesses of an absorbing layer into each ofthe stacks.

In the context of the present invention, where a layer is said to be an“absorbing layer” this means that the layer has measurable absorptionwithin the solar energy spectrum, including but not limited to thevisible part of the spectrum.

Certain absorbing layers are known in the prior art. For instance, EP0718250 A2 describes a coating stack with a protective metallic layer(e.g. Nb, Ta, Ti, Cr, Ni, NbTa, TaCr, or NiCr) located directly above afunctional metallic layer such as silver. The thickness of theprotective metallic layer may be modified to adjust the lighttransmission.

U.S. Pat. No. 4,816,054 A describes the coating of glass with singlemetal silicide functional layers (see claim 1) and specifically mentionsthe use of FeSi₂, NiSi and NiSi₂. No mention is made of other ironsilicide layers or particular locations of metal silicide layers inmultilayer stacks (the examples are all single coatings).

US 2005196632 A1 describes protective layers of, e.g., Zr silicide. Feand Ni silicides are mentioned but no specific examples are given (seeparagraph [0031]).

DETAILED DESCRIPTION OF THE INVENTION

According to a first aspect of the present invention there is provided acoated glass pane comprising at least the following layers:

a glass substrate; andat least one absorbing layer based on at least one metal silicide and/ormetal silicide nitride wherein the at least one absorbing layer isembedded between and contacts two layers based on an (oxi)nitride of Siand/or an (oxi)nitride of Al and/or alloys thereof.

The present invention provides multilayer coated glass panes thatinclude an absorbing layer which enables the optical properties, such assolar energy and/or light transmittance, of the panes to be fine tunedaccording to the thickness of the absorbing layer. The arrangement ofthe present invention enables high solar energy and/or light absorptioneven when relatively thin absorbing layers are used. Thicker absorbinglayers are undesirable from a manufacturing standpoint because of theneed to use higher power with the cathode target (this is expensive),use multiple cathode targets (this is expensive and inconvenient) and/orreduce the line speed (this adversely affects production volumes).

The panes of the present invention exhibit low haze and preferablyrelatively neutral transmitted or reflected colours before and afterheat treatment (the test was to heat a 4 mm thick sample at 650° C. for5 minutes). Indeed, the optical properties overall undergo minimalchanges during heat treatment which is of course advantageous from amanufacturing perspective.

In the following discussion of the invention, unless stated to thecontrary, the disclosure of alternative values for the upper or lowerlimit of the permitted range of a parameter, coupled with an indicationthat one of said values is more highly preferred than the other, is tobe construed as an implied statement that each intermediate value ofsaid parameter, lying between the more preferred and the less preferredof said alternatives, is itself preferred to said less preferred valueand also to each value lying between said less preferred value and saidintermediate value.

In the context of the present invention, where a layer is said to be“based on” a particular material or materials, this means that the layerpredominantly consists of the corresponding said material or materials,which means typically that it comprises at least about 50 at. % of saidmaterial or materials.

The at least one absorbing layer may comprise a layer based on asilicide and/or a silicide nitride of a metal or metal alloy from theelements selected from titanium, vanadium, chromium, manganese, iron,cobalt, nickel, zirconium, hafnium, niobium, tantalum, molybdenum,tungsten and/or aluminium.

The at least one absorbing layer may comprise a layer based on TiSi,TiSi₂, Ti₅Si₃, V₃Si, V₂Si, VSi, Cr₃Si, Cr₂Si, CrSi, CrSi₂, MnSi₂,FeSi_(n), where n is any integer or fraction from 1 to 9, Fe_(m)Si,where m is any integer or fraction from 1 to 9, CoSi₂, Ni₂Si, NiSi,NiSi₂, NiSi₆, NiCrSi₂, Zr₄Si, Zr₂Si, Zr₃Si₂, Zr₄Si₃, Zr₆Si₅, ZrSi,ZrSi₂, HfSi, HfSi₂, Nb₂Si, NbSi₂, Ta₅Si, Ta₅Si₂, Ta₅Si₃, TaSi₂, Mo₃Si,Mo₃Si₂, MoSi₂, W₃Si₂, WSi₂, Al₄Si₃ and/or AlSi₂ and/or nitrides thereof.

Where the at least one absorbing layer is based on FeSi_(n) and/ornitrides thereof, preferably n is any integer or fraction from 1 to 5,more preferably from 1 to 4. For example, the at least one absorbinglayer may be based on Fe₂Si₃.

Where the at least one absorbing layer is based on Fe_(m)Si and/ornitrides thereof, preferably m is any integer or fraction from 2 to 5,more preferably from 2 to 4, such as 3. For example, the at least oneabsorbing layer may be based on Fe₃Si.

The at least one absorbing layer may comprise a layer based on asilicide and/or a silicide nitride of a metal or metal alloy from theelements with atomic numbers 22 to 28.

According to a second aspect of the present invention there is provideda coated glass pane comprising at least the following layers:

a glass substrate; andat least one absorbing layer based on one or more of Fe₂Si₃, FeSi_(n),where n is any integer or fraction greater than or equal to 1 but lessthan 2 or greater than 2 but up to 9, and/or Fe_(m)Si, where m is anyinteger or fraction from 1 to 9, and/or nitrides thereof.

The second aspect of the present invention provides single or multilayercoated glass panes that include an iron silicide absorbing layer whichenables the energetic and/or optical properties, such as solar energyand/or light transmittance, of the panes to be fine tuned according tothe thickness of the absorbing layer. The arrangement of the secondaspect of the present invention enables high solar energy and/or lightabsorption even when relatively thin absorbing layers are used. Thepanes of the second aspect of the present invention also exhibit lowhaze and preferably relatively neutral transmitted or reflected coloursbefore and after heat treatment. Indeed, the optical properties overallundergo minimal changes during heat treatment.

In the second aspect of the present invention, where the at least oneabsorbing layer is based on FeSi_(n) and/or nitrides thereof, preferablyn is any integer or fraction from 1 to 1.95 or greater than 2.05 but upto 9, more preferably from 1 to 1.90 or greater than 2.10 but up to 9,even more preferably from 1 to 1.8 or greater than 2.2 but up to 9, evenmore preferably from 1 to 1.6 or greater than 2.5 but up to 9.Preferably n is at most 6, more preferably at most 5, even morepreferably at most 4.

In the second aspect of the present invention, where the at least oneabsorbing layer is based on Fe_(m)Si and/or nitrides thereof, preferablym is any integer or fraction from 2 to 5, more preferably from 2 to 4,such as 3.

In the second aspect of the present invention, preferably the at leastone absorbing layer is based on one or more of Fe₂Si₃, FeSi_(n), where nis any integer or fraction greater than or equal to 1 but less than 2 orgreater than 2 but up to 9, and/or Fe_(m)Si, where m is any integer orfraction from 1 to 9. Tests have shown that panes coated with a thinlayer of these iron silicides exhibit comparable solar energy and/orlight absorption to panes that are coated with much thicker layers ofthe corresponding iron silicide nitride, or NiSi₂ or NiSiN_(x). Asdetailed above, thicker absorbing layers are undesirable from amanufacturing standpoint because of the need to use higher power withthe cathode target (this is expensive), use multiple cathode targets(this is expensive and inconvenient) and/or reduce the line speed (thisadversely affects production volumes).

In the second aspect of the present invention, preferably the at leastone absorbing layer is based on Fe₂Si₃.

In the second aspect of the present invention, preferably the at leastone absorbing layer contacts at least one layer based on an (oxi)nitrideof Si and/or an (oxi)nitride of Al and/or alloys thereof. Morepreferably the at least one absorbing layer is embedded between andcontacts two layers based on an (oxi)nitride of Si and/or an(oxi)nitride of Al and/or alloys thereof. This arrangement is beneficialin terms of exhibiting the lowest haze and having the potential toachieve the most neutral transmitted or reflected colours before andafter heat treatment.

The following optional features are applicable to all aspects of thepresent invention in any combination and in any number:

Preferably the at least one absorbing layer contacts at least one layerbased on a nitride of Al. More preferably the at least one absorbinglayer is embedded between and contacts two layers based on a nitride ofAl.

Preferably the pane further comprises a silver-based functional layer.

Preferably the pane further comprises a lower anti-reflection layerlocated between the glass substrate and the silver-based functionallayer.

Preferably the pane further comprises an upper anti-reflection layerlocated above the silver-based functional layer.

In some embodiments the pane comprises more than one silver-basedfunctional layer. For example, the pane may comprise two, three or moresilver-based functional layers. When the pane comprises more than onesilver-based functional layer, each silver-based functional layer may bespaced apart from an adjacent silver-based functional layer by a centralanti-reflection layer. By providing more than one silver-basedfunctional layer, the functional layers may be spaced by interveningdielectric layers (=central anti-reflection layers) to form aFabry-Perot interference filter, whereby the optical properties of thelow-e and/or solar control coating may be further optimized for therespective application, as is well known in the art.

The at least one absorbing layer may be located in the loweranti-reflection layer, the upper anti-reflection layer and/or a centralanti-reflection layer of a coating comprising two or more silver-basedfunctional layers. Preferably the at least one absorbing layer islocated in the upper anti-reflection layer and/or a centralanti-reflection layer. These locations are advantageous in terms ofminimising the haze and providing the most neutral colours after a heattreatment. More preferably the at least one absorbing layer is locatedin a central anti-reflection layer. A central anti-reflection layer isthe best location in terms of low haze and neutral colours after a heattreatment.

The at least one absorbing layer may preferably have a thickness of atleast 0.5 nm, more preferably at least 1 nm, even more preferably atleast 2 nm, most preferably at least 3 nm; but preferably at most 12 nm,more preferably at most 10 nm, even more preferably at most 9 nm, mostpreferably at most 8 nm. As detailed above, thinner absorbing layers aredesirable for a number of reasons.

The layer(s) based on an (oxi)nitride of Si and/or an (oxi)nitride of Aland/or alloys thereof may each independently preferably have a thicknessof at least 3 nm, more preferably at least 5 nm, even more preferably atleast 6 nm, most preferably at least 7 nm; but preferably at most 30 nm,more preferably at most 25 nm, even more preferably at most 21 nm, mostpreferably at most 19 nm.

The lower anti-reflection layer of a coating comprising at least onesilver-based functional layer may comprise at least a combination of oneor more of the following layers:

a base layer based on an (oxi)nitride of Si and/or an (oxi)nitride of Aland/or alloys thereof; and/or an oxide of Ti; and/or an oxide of Zr;a layer based on a metal oxide, such as an oxide of Zn and Sn and/or anoxide of Sn;a separation layer based on a metal oxide and/or an (oxi)nitride of Siand/or an (oxi)nitride of Al and/or alloys thereof; anda top layer based on an oxide of Zn.

Preferably the lower anti-reflection layer comprises at least, insequence from the glass substrate,

-   -   a base layer based on an (oxi)nitride of Si and/or an        (oxi)nitride of Al and/or alloys thereof; and/or an oxide of Ti;        and/or an oxide of Zr;    -   a layer based on a metal oxide, such as an oxide of Zn and Sn        and/or an oxide of Sn; and    -   a top layer based on an oxide of Zn.

The lower anti-reflection layer may consist of the three layers insequence as set out above.

In some embodiments the lower anti-reflection layer comprises, insequence from the glass substrate,

-   -   a base layer based on an (oxi)nitride of Si and/or an        (oxi)nitride of Al and/or alloys thereof; and/or an oxide of Ti;        and/or an oxide of Zr;    -   a layer based on a metal oxide, such as an oxide of Zn and Sn        and/or an oxide of Sn;    -   a separation layer based on a metal oxide and/or an (oxi)nitride        of Si and/or an (oxi)nitride of Al and/or alloys thereof; and    -   a top layer based on an oxide of Zn.

The base layer based on an (oxi)nitride of Si and/or an (oxi)nitride ofAl and/or alloys thereof; and/or an oxide of Ti; and/or an oxide of Zrof the lower anti-reflection layer may have a thickness of at least 5nm, preferably from 5 to 60 nm, more preferably from 10 to 50 nm, evenmore preferably from 20 to 45 nm, most preferably from 30 to 40 nm. Thisbase layer serves as a glass side diffusion barrier amongst other uses.

The term “(oxi)nitride of Si” encompasses both Si nitride (SiN_(x)) andSi oxinitride (SiO_(x)N_(y)) whilst the term “(oxi)nitride of Al”encompasses both Al nitride (AlN_(x)) and Al oxinitride (AlO_(x)N_(y)).Si nitride, Si oxinitride, Al nitride and Al oxinitride layers arepreferably essentially stoichiometric (e.g. Si nitride=Si₃N₄, x=1.33)but may also be substoichiometric or even super-stoichiometric, as longas the heat treatability of the coating is not negatively affectedthereby. One preferred composition of the base layer based on an(oxi)nitride of Si and/or an (oxi)nitride of Al and/or alloys thereof ofthe lower anti-reflection layer is an essentially stoichiometric mixednitride Si₉₀Al₁₀N_(x).

Layers of an (oxi)nitride of Si and/or an (oxi)nitride of Al and/oralloys thereof may be reactively sputtered from Si- and/or Al-basedtargets respectively in a sputtering atmosphere containing nitrogen andargon. An oxygen content of the base layer based on an (oxi)nitride ofSi and/or an (oxi)nitride of Al and/or alloys thereof may result fromresidual oxygen in the sputtering atmosphere or from a controlledcontent of added oxygen in said atmosphere. It is generally preferred ifthe oxygen content of the Si (oxi)nitride and/or Al (oxi)nitride issignificantly lower than its nitrogen content, i.e. if the atomic ratioO/N in the layer is kept significantly below 1. It is most preferred touse Si nitride and/or Al nitride with negligible oxygen content for thebase layer of the lower anti-reflection layer. This feature may becontrolled by making sure that the refractive index of the layer doesnot differ significantly from the refractive index of an oxygen-free Sinitride and/or Al nitride layer.

It is within the scope of the invention to use mixed Si and/or Altargets or to otherwise add metals or semiconductors to the Si and/or Alcomponent of this layer as long as the essential barrier and protectionproperty of the base layer of the lower anti-reflection layer is notlost. It is well known and established to mix Al with Si targets, othermixed targets not being excluded. Additional components may be typicallypresent in amounts of up to about 10-15 wt. %. Al is usually present inmixed Si targets in an amount of about 10 wt. %.

The at least one absorbing layer may be embedded in the base layer basedon an (oxi)nitride of Si and/or an (oxi)nitride of Al and/or alloysthereof of the lower anti-reflection layer.

The base layer of the lower anti-reflection layer may be based onTiO_(x) and/or ZrO_(x) where x is from 1.5 to 2.0.

The layer based on a metal oxide, such as an oxide of Zn and Sn and/oran oxide of Sn of the lower anti-reflection layer serves to improvestability during a heat treatment by providing a dense and thermallystable layer and contributing to reduce the haze after a heat treatment.The layer based on a metal oxide, such as an oxide of Zn and Sn and/oran oxide of Sn of the lower anti-reflection layer may have a thicknessof at least 0.5 nm, preferably from 0.5 to 10 nm, more preferably from0.5 to 9 nm, even more preferably from 1 to 8 nm, even more preferablyfrom 1 to 7 nm, even more preferably from 2 to 6 nm, even morepreferably from 3 to 6 nm, most preferably from 3 to 5 nm. An upperthickness limit of about 8 nm is preferred due to optical interferenceconditions and by a reduction of heat treatability due to the resultingreduction in the thickness of the base layer that would be needed tomaintain the optical interference boundary conditions foranti-reflecting the functional layer.

The layer based on a metal oxide, such as an oxide of Zn and Sn and/oran oxide of Sn of the lower anti-reflection layer is preferably locateddirectly on the base layer based on an (oxi)nitride of Si and/or an(oxi)nitride of Al and/or alloys thereof.

The layer based on an oxide of Zn and Sn (abbreviation: ZnSnO_(x)) ofthe lower anti-reflection layer preferably comprises about 10-90 wt. %Zn and 90-10 wt. % Sn, more preferably about 40-60 wt. % Zn and about40-60 wt. % Sn, preferably about 50 wt. % each of Zn and Sn, in wt. % ofits total metal content. In some preferred embodiments the layer basedon an oxide of Zn and Sn of the lower anti-reflection layer may compriseat most 18 wt. % Sn, more preferably at most 15 wt. % Sn, even morepreferably at most 10 wt. % Sn. The layer based on an oxide of Zn and Snmay be deposited by reactive sputtering of a mixed ZnSn target in thepresence of O₂.

The separation layer based on a metal oxide and/or an (oxi)nitride ofsilicon and/or an (oxi)nitride of aluminium and/or alloys thereof mayhave a thickness of at least 0.5 nm, preferably from 0.5 to 6 nm, morepreferably from 0.5 to 5 nm, even more preferably from 0.5 to 4 nm, mostpreferably from 0.5 to 3 nm. These preferred thicknesses enable furtherimprovement in haze upon heat treatment. The separation layer providesprotection during the deposition process and during a subsequent heattreatment. The separation layer is either essentially fully oxidisedimmediately after its deposition, or it oxidizes to an essentially fullyoxidized layer during deposition of a subsequent oxide layer.

When the separation layer is based on an (oxi)nitride of silicon and/oran (oxi)nitride of aluminium and/or alloys thereof, the at least oneabsorbing layer may be embedded in the separation layer.

The separation layer may be deposited using non-reactive sputtering froma ceramic target based on for instance a slightly substoichiometrictitanium oxide, for example a TiO_(1.98) target, as an essentiallystoichiometric or as a slightly substoichiometric oxide, by reactivesputtering of a target based on Ti in the presence of O₂, or bydepositing a thin layer based on Ti which is then oxidised. In thecontext of the present invention, an “essentially stoichiometric oxide”means an oxide that is at least 95% but at most 105% stoichiometric,whilst a “slightly substoichiometric oxide” means an oxide that is atleast 95% but less than 100% stoichiometric.

When the separation layer is based on a metal oxide said separationlayer may comprise a layer based on an oxide of Ti, NiCr, InSn, Zr, Aland/or Si.

In addition to the metal oxide and/or (oxi)nitride of silicon and/or(oxi)nitride of aluminium and/or alloys thereof on which it is based,the separation layer may further include one or more other chemicalelements chosen from at least one of the following elements Ti, V, Mn,Co, Cu, Zn, Zr, Hf, Al, Nb, Ni, Cr, Mo, Ta, Si or from an alloy based onat least one of these materials, used for instance as dopants oralloyants.

The top layer based on an oxide of Zn primarily functions as a growthpromoting layer for a subsequently deposited silver-based functionallayer. The top layer based on an oxide of Zn is optionally mixed withmetals such as Al or Sn in an amount of up to about 10 wt. % (wt. %referring to the target metal content). A typical content of said metalssuch as Al or Sn is about 2 wt. %, Al being actually preferred. ZnO andmixed Zn oxides have proven very effective as a growth promoting layerthat assists in achieving a low sheet resistance at a given thickness ofthe subsequently deposited silver-based functional layer. It ispreferred if the top layer of the lower anti-reflection layer isreactively sputtered from a Zn target in the presence of O₂ or if it isdeposited by sputtering a ceramic target, e.g. based on ZnO:Al, in anatmosphere containing no or only a low amount, generally no more thanabout 5 vol. %, of oxygen. The top layer based on an oxide of Zn mayhave a thickness of at least 2 nm, preferably from 2 to 15 nm, morepreferably from 4 to 12 nm, even more preferably from 5 to 10 nm, evenmore preferably from 5 to 9 nm.

The silver-based functional layer(s) may consist essentially of silverwithout any additive, as is normally the case in the area of low-eand/or solar control coatings. It is, however, within the scope of theinvention to modify the properties of the silver-based functionallayer(s) by adding doping agents, alloy additives or the like or evenadding very thin metal or metal compound layers, as long as theproperties of the silver-based functional layer(s) necessary for its(their) function as highly light-transmitting and low light-absorbentIR-reflective layer(s) are not substantially impaired thereby.

The thickness of a silver-based functional layer is dominated by itstechnical purpose. For typical low-e and/or solar control purposes thepreferred layer thickness for a single silver-based layer is from 5 to20 nm, more preferably from 5 to 15 nm, even more preferably from 5 to12 nm, even more preferably from 7 to 11 nm, most preferably from 8 to10 nm. With such a layer thickness light transmittance values of above86% and a normal emissivity below 0.05 after a heat treatment can beeasily achieved for single silver coatings. If better solar controlproperties are aimed at the thickness of the silver-based functionallayer may be adequately increased or several spaced functional layersmay be provided.

When the pane comprises two silver-based functional layers, thesilver-based functional layer located furthest from the glass substratemay preferably have a thickness of from 5 to 25 nm, more preferably from10 to 21 nm, even more preferably from 13 to 19 nm, even more preferablyfrom 14 to 18 nm, most preferably from 15 to 17 nm.

When the pane comprises three silver-based functional layers, the twosilver-based functional layers located furthest from the glass substratemay each independently preferably have a thickness of from 5 to 25 nm,more preferably from 10 to 21 nm, even more preferably from 13 to 19 nm,even more preferably from 14 to 18 nm, most preferably from 15 to 17 nm.

Preferably the top layer based on an oxide of Zn in the loweranti-reflection layer is in direct contact with the silver-basedfunctional layer.

The central anti-reflection layer(s) may comprise at least a combinationof one or more of the following layers: a layer based on an oxide of Znand/or an oxide of Ti;

a layer based on an oxide of NiCr;a layer based on a metal oxide, such as an oxide of Zn and Sn and/or anoxide of Sn; anda layer based on an (oxi)nitride of Si, and/or an (oxi)nitride of Al,and/or alloys thereof, and/or an oxide of Al, Si, Ti, and/or Zr.

In some preferred embodiments each silver-based functional layer isspaced apart from an adjacent silver-based functional layer by a centralanti-reflection layer,

wherein each central anti-reflection layer comprises at least,in sequence from the silver-based functional layer that is locatednearest to the glass substrate out of the silver-based functional layersthat the central anti-reflection layer is located between,a barrier layer based on an oxide of Zn;a layer based on a metal oxide, such as an oxide of Zn and Sn and/or anoxide of Sn;a layer based on an (oxi)nitride of Si, and/or an (oxi)nitride of Al,and/or alloys thereof, and/or an oxide of Al, Si, Ti, and/or Zr, anda top layer based on an oxide of Zn.

In some other preferred embodiments each silver-based functional layeris spaced apart from an adjacent silver-based functional layer by acentral anti-reflection layer,

wherein each central anti-reflection layer comprises at least,in sequence from the silver-based functional layer that is locatednearest to the glass substrate out of the silver-based functional layersthat the central anti-reflection layer is located between,a barrier layer based on an oxide of NiCr;a barrier layer based on an oxide of Zn;a layer based on an (oxi)nitride of Si, and/or an (oxi)nitride of Al,and/or alloys thereof, and/or an oxide of Al, Si, Ti, and/or Zr,a layer based on a metal oxide, such as an oxide of Zn and Sn and/or anoxide of Sn; anda top layer based on an oxide of Zn.

The at least one absorbing layer may be embedded in the layer based onan (oxi)nitride of Si and/or an (oxi)nitride of Al and/or alloys thereofof a central anti-reflection layer.

The layer based on an oxide of NiCr may preferably have a thickness ofat least 0.3 nm, more preferably at least 0.4 nm, even more preferablyat least 0.5 nm, most preferably at least 0.6 nm; but preferably at most5 nm, more preferably at most 2 nm, even more preferably at most 1 nm,most preferably at most 0.9 nm. These preferred thicknesses enablefurther ease of deposition and improvement in optical characteristicssuch as haze whilst retaining mechanical durability.

The layer(s) based on an oxide of Zn and/or an oxide of Ti of thecentral anti-reflection layer may independently preferably have athickness of at least 1 nm, more preferably at least 2 nm, even morepreferably at least 3 nm, most preferably at least 3.5 nm; butpreferably at most 10 nm, more preferably at most 7 nm, even morepreferably at most 5 nm, most preferably at most 4 nm. These preferredthicknesses enable further ease of deposition and improvement in opticalcharacteristics such as haze whilst retaining mechanical durability.

The layer based on a metal oxide, such as an oxide of Zn and Sn and/oran oxide of Sn of the central anti-reflection layer may preferably havea thickness of at least 5 nm, more preferably at least 10 nm, even morepreferably at least 13 nm, most preferably at least 14 nm; butpreferably at most 40 nm, more preferably at most 30 nm, even morepreferably at most 25 nm, most preferably at most 21 nm.

The layer based on an (oxi)nitride of Si, and/or an (oxi)nitride of Al,and/or alloys thereof, and/or an oxide of Al, Si, Ti, and/or Zr of thecentral anti-reflection layer may preferably have a thickness of atleast 5 nm, more preferably at least 15 nm, even more preferably atleast 25 nm, most preferably at least 30 nm; but preferably at most 60nm, more preferably at most 50 nm, even more preferably at most 45 nm,most preferably at most 40 nm.

The upper anti-reflection layer may comprise at least a combination ofone or more of the following layers: a layer based on an oxide of NiCr;

a layer based on an oxide of Zn and/or an oxide of Ti;a layer based on an (oxi)nitride of Si, and/or an (oxi)nitride of Al,and/or alloys thereof, and/or an oxide of Al, Si, Ti, and/or Zr; anda layer based on a metal oxide, such as an oxide of Zn and Sn and/or anoxide of Sn.

In some preferred embodiments the upper anti-reflection layer comprisesat least, in sequence from the silver-based functional layer that islocated furthest from the glass substrate,

a barrier layer based on an oxide of Zn;a layer based on an (oxi)nitride of Si, and/or an (oxi)nitride of Al,and/or alloys thereof, and/or an oxide of Al, Si, Ti, and/or Zr; anda layer based on a metal oxide, such as an oxide of Zn and Sn and/or anoxide of Sn.

In some other preferred embodiments the upper anti-reflection layercomprises at least, in sequence from the silver-based functional layerthat is located furthest from the glass substrate,

a barrier layer based on an oxide of NiCr;a barrier layer based on an oxide of Zn;a layer based on an (oxi)nitride of Si, and/or an (oxi)nitride of Al,and/or alloys thereof, and/or an oxide of Al, Si, Ti, and/or Zr, anda layer based on a metal oxide, such as an oxide of Zn and Sn and/or anoxide of Sn.

The at least one absorbing layer may be embedded in the layer based onan (oxi)nitride of Si and/or an (oxi)nitride of Al and/or alloys thereofof the upper anti-reflection layer.

The barrier layer based on an oxide of Zn and/or an oxide of Ti of theupper anti-reflection layer may preferably have a thickness of at least1 nm, more preferably at least 2 nm, even more preferably at least 3 nm,most preferably at least 3.5 nm; but preferably at most 10 nm, morepreferably at most 7 nm, even more preferably at most 5 nm, mostpreferably at most 4 nm. These preferred thicknesses enable further easeof deposition and improvement in optical characteristics such as hazewhilst retaining mechanical durability.

It has been found that a superior protection of the silver-basedfunctional layer(s) during the deposition process and a high opticalstability during a heat treatment can be achieved if the barrier layercomprises a layer of a mixed metal oxide sputtered from a mixed metaloxide target. When the barrier layer is based on an oxide of Zn, saidoxide may be a mixed metal oxide such as ZnO:Al. Good results areparticularly achieved if a layer based on ZnO:Al is sputtered from aconductive ZnO:Al target. ZnO:Al may be deposited fully oxidized or suchthat it is slightly suboxidic. Preferably the ZnO:Al barrier layer isessentially stoichiometric. The use of essentially stoichiometric ZnO:Albarrier layers rather than metallic or less than 95% stoichiometricZnO:Al barrier layers leads to an extremely high optical stability ofthe coating during a heat treatment and effectively assists in keepingoptical modifications during a heat treatment small. Additionally theuse of barrier layers based on essentially stoichiometric metal oxidesprovides benefits in terms of mechanical robustness.

When the barrier layer is based on an oxide of NiCr it is preferablydeposited as a substoichiometric oxide. This enables the layer to act asan oxygen scavenger/absorber during a heat treatment.

At least a portion of a barrier layer that is in direct contact with asilver-based functional layer is preferably deposited using non-reactivesputtering of an oxidic target to avoid silver damage.

Preferably the barrier layers are deposited by non-reactive sputtering.Preferably the barrier layers are sputtered from ceramic targets. In thecontext of the present invention the term “non-reactive sputtering”includes sputtering an oxidic target in a low oxygen atmosphere (no orup to 5 vol. % oxygen) to provide an essentially stoichiometric oxide.

Where a barrier layer is based on TiO_(x), x may be from 1.5 to 2.0.

The layer based on an (oxi)nitride of Si, and/or an (oxi)nitride of Al,and/or alloys thereof, and/or an oxide of Al, Si, Ti, and/or Zr of theupper anti-reflection layer may preferably have a thickness of at least2 nm, more preferably at least 5 nm, even more preferably at least 10nm, most preferably at least 15 nm; but preferably at most 40 nm, morepreferably at most 35 nm, even more preferably at most 30 nm, mostpreferably at most 25 nm. Such thicknesses provide further improvementin terms of mechanical robustness of the coated pane. Said layer basedon an (oxi)nitride of Si, and/or an (oxi)nitride of Al, and/or alloysthereof, and/or an oxide of Al, Si, Ti, and/or Zr may preferably be indirect contact with the barrier layer.

The layer based on an (oxi)nitride of Si, and/or an (oxi)nitride of Al,and/or alloys thereof, and/or an oxide of Al, Si, Ti, and/or Zr, whichcan in some cases make up a major part of the upper anti-reflectionlayer, provides stability (better protection during heat treatments) anddiffusion barrier properties. Said layer is preferably deposited as anAl nitride and/or Si nitride layer by reactive sputtering of a Si, Al ormixed SiAl target, e.g. of a Si₉₀Al₁₀ target in a N₂ containingatmosphere. The composition of the layer based on an (oxi)nitride of Aland/or an (oxi)nitride of Si may be essentially stoichiometricSi₉₀Al₁₀N_(x).

The layer based on a metal oxide, such as an oxide of Zn and Sn and/oran oxide of Sn of the upper anti-reflection layer may preferably have athickness of at least 1 nm, more preferably at least 5 nm, even morepreferably at least 7 nm, most preferably at least 9 nm; but preferablyat most 20 nm, more preferably at most 15 nm, even more preferably atmost 13 nm, most preferably at most 11 nm. Such thicknesses providefurther improvement in terms of mechanical robustness of the coatedpane. When said layer is an oxide of Zn and Sn it preferably comprisesabout 10-90 wt. % Zn and 90-10 wt. % Sn, more preferably about 40-60 wt.% Zn and about 40-60 wt. % Sn, preferably about 50 wt. % each of Zn andSn, in wt. % of its total metal content. In some preferred embodimentssaid layer based on an oxide of Zn and Sn of the upper anti-reflectionlayer may comprise at most 18 wt. % Sn, more preferably at most 15 wt. %Sn, even more preferably at most 10 wt. % Sn. Said layer may bedeposited by reactive sputtering of a mixed ZnSn target in the presenceof O₂ and contributes to the anti-reflection properties of the upperanti-reflection layer.

The layer based on an (oxi)nitride of Si, and/or an (oxi)nitride of Al,and/or alloys thereof, and/or an oxide of Al, Si, Ti, and/or Zr of theupper anti-reflection layer may be in direct contact with the layerbased on a metal oxide of the upper anti-reflection layer as definedherein without any intervening further dielectric layer.

Preferably the layer based on a metal oxide of the upper anti-reflectionlayer comprises a layer based on an oxide of Zn and Sn and/or an oxideof Sn.

The upper anti-reflection layer may have a total thickness of from 20 to60 nm, preferably from 25 to 50 nm, more preferably from 30 to 50 nm,even more preferably from 35 to 45 nm.

A protective layer may be deposited as a top layer (outermost layer) ofthe upper anti-reflection layer for increased mechanical and/or chemicalrobustness, e.g. scratch resistance. Said protective layer may comprisea layer based on an oxide of Al, Si, Ti, and/or Zr.

To reduce the light transmittance increase during a heat treatment allindividual layers of the upper, central and lower anti-reflection layersare preferably deposited with an essentially stoichiometric composition.

To further optimize the optical properties of the coated pane the upperand/or lower anti-reflection layers may comprise further partial layersconsisting of suitable materials generally known for dielectric layersof low-e and/or solar control coatings, in particular chosen from one ormore of the oxides of Sn, Ti, Zn, Nb, Ce, Hf, Ta, Zr, Al and/or Siand/or of (oxi)nitrides of Si and/or Al or combinations thereof. Whenadding such further partial layers it should however be verified thatthe heat treatability aimed at herein is not impaired thereby.

It will be appreciated that any further partial layer may containadditives that modify its properties and/or facilitate its manufacture,e.g. doping agents or reaction products of reactive sputtering gases. Inthe case of oxide based layers nitrogen may be added to the sputteringatmosphere leading to the formation of oxinitrides rather than oxides,in the case of nitride based layers oxygen may be added to thesputtering atmosphere, also leading to the formation of oxinitridesrather than nitrides.

Care must be taken by performing a proper material, structure andthickness selection when adding any such further partial layer to thebasic layer sequence of the inventive pane that the properties primarilyaimed at, e.g. a high thermal stability, are not significantly impairedthereby.

The invention is not limited to a specific production process for thecoating. However, it is particularly preferred if at least one of thelayers and most preferably all layers are applied by magnetron cathodesputtering, either in the DC mode, in the pulsed mode, in the mediumfrequency mode or in any other suitable mode, whereby metallic orsemiconducting targets are sputtered reactively or non-reactively in asuitable sputtering atmosphere. Depending on the materials to besputtered planar or rotating tubular targets may be used.

The coating process is preferably carried out by setting up suitablecoating conditions such that any oxygen (or nitrogen) deficit of anyoxide (or nitride) layer of the anti-reflection layers of the coating iskept low to achieve a high stability of the light transmittance andcolour of the coated glass panes during a heat treatment.

Light transmittance values referred to in the specification aregenerally specified with reference to a coated glass pane comprising a 4mm thick standard float glass pane having a light transmittance TL of89% without a coating.

The thermal stability of coated glass panes according to the inventionis reflected by the fact that the heat treated coated glass panes do notexhibit unacceptable levels of haze. Large increases in the haze valueif detected during a heat treatment would indicate that the coating isbeginning to be damaged.

According to another aspect of the present invention there is provided amultiple glazing incorporating a coated glass pane in accordance withthe present invention. For example the multiple glazing may be laminatedglass or insulating glass.

It will be appreciated that optional features applicable to one aspectof the invention can be used in any combination, and in any number.Moreover, they can also be used with any of the other aspects of theinvention in any combination and in any number. This includes, but isnot limited to, the dependent claims from any claim being used asdependent claims for any other claim in the claims of this application.

The reader's attention is directed to all papers and documents which arefiled concurrently with or previous to this specification in connectionwith this application and which are open to public inspection with thisspecification, and the contents of all such papers and documents areincorporated herein by reference.

All of the features disclosed in this specification (including anyaccompanying claims, abstract and drawings), and/or all of the steps ofany method or process so disclosed, may be combined in any combination,except combinations where at least some of such features and/or stepsare mutually exclusive.

Each feature disclosed in this specification (including any accompanyingclaims, abstract and drawings) may be replaced by alternative featuresserving the same, equivalent or similar purpose, unless expressly statedotherwise. Thus, unless expressly stated otherwise, each featuredisclosed is one example only of a generic series of equivalent orsimilar features.

The invention will now be further described by way of the followingspecific embodiments, which are given by way of illustration and not oflimitation:

For all Examples the coatings were deposited on 4 mm thick standardfloat glass panes (10 cm×10 cm) with a light transmittance of about 89%using AC and/or DC magnetron sputtering devices, medium-frequencysputtering being applied where appropriate. Prior to coating, the glasswas washed twice on a Benteler® washing machine. All dielectric layersof an oxide of Zn and Sn (ZnSnO_(x), weight ratio Zn:Sn≈50:50) werereactively sputtered from zinc-tin targets in an Ar/O₂ sputteratmosphere.

The ZnO:Al growth promoting top layers of the lower anti-reflectionlayers were sputtered from Al-doped Zn targets (Al content about 2 wt.%) in an Ar/02 sputter atmosphere.

The functional layers that in all Examples consisted of essentially puresilver (Ag) were sputtered from silver targets in an Ar sputteratmosphere without any added oxygen and at a partial pressure ofresidual oxygen below 10⁻⁵ mbar.

The barrier layers of Al-doped zinc oxide (ZnO:Al, ZAO) were sputteredfrom conductive ZnOx:Al targets in a pure Ar sputter atmosphere withoutadded oxygen.

The layers of mixed silicon aluminium nitride (Si₉₀Al₁₀N_(x)) werereactively sputtered from mixed Si₉₀Al₁₀ targets in an Ar/N₂ sputteratmosphere containing only residual oxygen.

The layers of Al nitride were reactively sputtered from Al targets in anAr/N₂ sputter atmosphere containing only residual oxygen.

The layers of Fe₂Si₃ were reactively sputtered from Fe and Si targets ina pure Ar sputter atmosphere without added oxygen.

The layers of Fe₂Si₃N_(x) were reactively sputtered from Fe and Sitargets in an Ar/N₂ sputter atmosphere containing only residual oxygen.

The layers of NiSi₂ were reactively sputtered from Ni and Si targets ina pure Ar sputter atmosphere without added oxygen.

The layers of NiSi₂N_(x) were reactively sputtered from Ni and Sitargets in an Ar/N₂ sputter atmosphere containing only residual oxygen.

TABLE 1 Haze score, light transmittance and reflection properties for anumber of comparative coated glass panes and coated glass panesaccording to the present invention. Colour T Colour Rc Colour Rg ColourRg Stack (First Layer (HT) (HT) (AD) (HT) % T_(L) Deposited On Glass) a*b* Y a* b* a* b* Y a* b* AD HT Haze Example 1 (Comparative) −2.38 2.174.82 3.1 −13.95 1.39 −13.50 5.51 2.70 −13.88 86.48 88.18 0 AlN_(x) 16.1nm/ZnSnO_(x) 4.5 nm/ZAO 5 nm/Ag 9 nm/ ZAO 3 nm/AlN_(x) 21.6 nm/ZnSnO_(x) 10.1 nm Example 2 (Comparative) −4.75 1.23 6.1 10.15 0.65 6.51−4.66 6.20 7.39 −4.59 79.73 82.44 0/1 AlN_(x) 21 nm/ZnSnO_(x) 5 nm/ZAO 8nm/Ag 9 nm/ ZAO 3.8 nm/ZnSnO_(x) 37 nm/AlN_(x) 35 nm/ZAO 6.3 nm/Ag 16nm/ZAO 3.8 nm/AlN_(x) 21 nm/ZnSnO_(x) 10 nm Example 3 −6.12 1.3 16.79.65 0.51 −3.56 −4.25 9.5 −4.48 −4.43 40.07 43.27 1/2 AlN_(x) 21nm/ZnSnO_(x) 5 nm/ZAO 8 nm/Ag 9 nm/ZAO 3.8 nm/ZnSnO_(x) 37 nm/AlN_(x)17.5 nm/ Fe₂Si₃ 5 nm/AlN_(x) 17.5 nm/ZAO 6.3 nm/Ag 16 nm/ZAO 3.8nm/AlN_(x) 21 nm/ZnSnO_(x) 10 nm Example 4 −5.87 1.51 12.62 10.24 −1.63−3.41 −5.52 7.40 −3.41 −7.20 48.58 52.32 1/2 AlN_(x) 21 nm/ZnSnO_(x) 5nm/ZAO 8 nm/Ag 9 nm/ ZAO 3.8 nm/ZnSnO_(x) 37 nm/AlN_(x) 17.5 nm/Fe₂Si₃3.5 nm/AlN_(x) 17.5 nm/ ZAO 6.3 nm/Ag 16 nm/ ZAO 3.8 nm/AlN_(x) 21nm/ZnSnO_(x) 10 nm Example 5 −5.01 −1.22 5.68 14.79 2.76 −2.51 −11.738.74 −2.08 −8.11 52.31 60.96 2 AlN_(x) 21 nm/ZnSnO_(x) 5 nm/ZAO 8 nm/Ag9 nm/ ZAO 3.8 nm/ZnSnO_(x) 37 nm/Fe₂Si₃ 3.5 nm/AlN_(x) 35 nm/ZAO 6.3nm/Ag 16 nm/ZAO 3.8 nm/AlN_(x) 21 nm/ZnSnO_(x) 10 nm Example 6 −4.7 4.1621.96 4.85 −3.07 0.81 1.15 14.63 0.14 −1.4 53.9 55.63 2 AlN_(x) 21nm/ZnSnO_(x) 5 nm/ZAO 8 nm/Ag 9 nm/ ZAO 3.8 nm/ZnSnO_(x) 37 nm/AlN_(x)17.5 nm/ Fe₂Si₃N_(x) 14.5 nm/AlN_(x) 17.5 nm/ZAO 6.3 nm/Ag 16 nm/ZAO 3.8nm/AlN_(x) 21 nm/ZnSnO_(x) 10 nm Example 7 −6.1 5.69 2.81 −4.71 −0.718.66 −15.72 10.63 10.14 −15.70 49.91 56.25 1/2 AlN_(x) 21 nm/ZnSnO_(x) 5nm/ZAO 8 nm/Ag 9 nm/ ZAO 3.8 nm/ZnSnO_(x) 37 nm/AlN_(x) 35 nm/ZAO 6.3nm/Ag 16 nm/ZAO 3.8 nm/AlN_(x) 10.5 nm/Fe₂Si₃ 3.5 nm/AlN_(x) 10.5 nm/ZnSnO_(x) 10 nm Example 8 −3.75 12.75 5.95 8.41 −30.37 0.1 −29.53 15.372.59 −30.5 58.69 62.79 2 AlN_(x) 21 nm/ZnSnO_(x) 5 nm/ZAO 8 nm/Ag 9 nm/ZAO 3.8 nm/ZnSnO_(x) 37 nm/AlN_(x) 35 nm/ZAO 6.3 nm/Ag 16 nm/ZAO 3.8nm/AlN_(x) 10.5 nm/ Fe₂Si₃N_(x) 14.5 nm/AlN_(x) 10.5 nm/ZnSnO_(x) 10 nmExample 9 (Comparative) −3.64 1.09 9.01 −7.79 −4.9 −5.8 1.3 13.49 −9.35−1.73 58.53 69.56 4 AlN_(x) 21 nm/ZnSnO_(x) 5 nm/ZAO 8 nm/Ag 9 nm/ NiSi₂4 nm/ZAO 3.8 nm/ ZnSnO_(x) 37 nm/AlN_(x) 35 nm/ZAO 6.3 nm/Ag 16 nm/ZAO3.8 nm/AlN_(x) 21 nm/ZnSnO_(x) 10 nm Example 10 (Comparative) −4.12−3.22 19.67 −0.36 10.4 1.81 −8.75 6.73 −1.33 −6.29 51.78 54.69 2/3AlN_(x) 21 nm/ZnSnO_(x) 5 nm/ZAO 8 nm/Ag 9 nm/ ZAO 3.8 nm/ZnSnO_(x) 37nm/AlN_(x) 35 nm/NiSi₂ 4.5 nm/ZAO 6.3 nm/Ag 16 nm/ZAO 3.8 nm/AlN_(x) 21nm/ZnSnO_(x) 10 nm Example 11 −4.29 −4.06 17.83 3.09 10.24 −3.75 2.326.43 −6.66 2.85 48.54 51.51 2 AlN_(x) 21 nm/ZnSnO_(x) 5 nm/ZAO 8 nm/Ag 9nm/ ZAO 3.8 nm/ZnSnO_(x) 37 nm/AlN_(x) 17.5 nm/NiSi₂ 4.0 nm/AlN_(x) 17.5nm/ ZAO 6.3 nm/Ag 16 nm/ ZAO 3.8 nm/AlN_(x) 21 nm/ZnSnO_(x) 10 nmExample 12 −4.25 −3.32 16.63 4.59 4.97 −1.87 −0.54 7.5 −4.44 0.48 52.5155.83 2 AlN_(x) 21 nm/ZnSnO_(x) 5 nm/ZAO 8 nm/Ag 9 nm/ ZAO 3.8nm/ZnSnO_(x) 37 nm/AlN_(x) 17.5 nm/NiSi₂ 3.7 nm/AlN_(x) 17.5 nm/ ZAO 6.3nm/Ag 16 nm/ ZAO 3.8 nm/AlN_(x) 21 nm/ZnSnO_(x) 10 nm Example 13 −4.2−2.56 17.18 1.79 7.37 −0.13 −2.77 6.15 −2.56 −1.06 52.84 55.93 1/2AlN_(x) 21 nm/ZnSnO_(x) 5 nm/ZAO 8 nm/Ag 9 nm/ ZAO 3.8 nm/ZnSnO_(x) 37nm/AlN_(x) 27.5 nm/NiSi₂ 4.0 nm/AlN_(x) 7.5 nm/ZAO 6.3 nm/Ag 16 nm/ZAO3.8 nm/AlN_(x) 21 nm/ ZnSnO_(x) 10 nm Example 14 −5.04 −1.71 15.08 6.4210.04 −4.27 0.85 8.95 −7 1.14 47.06 50.64 1 AlN_(x) 21 nm/ZnSnO_(x) 5nm/ZAO 8 nm/Ag 9 nm/ ZAO 3.8 nm/ZnSnO_(x) 37 nm/AlN_(x) 7.5 nm/NiSi₂ 4.0nm/AlN_(x) 27.5 nm/ ZAO 6.3 nm/Ag 16 nm/ ZAO 3.8 nm/AlN_(x) 21nm/ZnSnO_(x) 10 nm Example 15 −4.53 −2.41 17.36 4.56 3.1 −1.43 0.01 7.09−3.49 0.38 48.57 54.42 2 AlN_(x) 21 nm/ZnSnO_(x) 5 nm/ZAO 8 nm/Ag 9 nm/ZAO 3.8 nm/ZnSnO_(x) 37 nm/AlN_(x) 20 nm/NiSi₂ 4.0 nm/AlN_(x) 15 nm/ZAO6.3 nm/Ag 16 nm/ZAO 3.8 nm/AlN_(x) 21 nm/ZnSnO_(x) 10 nm Example 16−4.24 −2.59 18.57 3.61 2.43 0.42 −2.31 6.45 −1.59 −1.77 51.29 54.24 2AlN_(x) 21 nm/ZnSnO_(x) 5 nm/ZAO 8 nm/Ag 9 nm/ ZAO 3.8 nm/ZnSnO_(x) 37nm/AlN_(x) 25 nm/NiSi₂ 4.2 nm/AlN_(x) 10 nm/ZAO 6.3 nm/Ag 16 nm/ZAO 3.8nm/AlN_(x) 21 nm/ZnSnO_(x) 10 nm Example 17 −4.26 −1.58 20.48 4.17 9.06−1.38 3.84 11.79 −1.52 6.04 54.92 54.54 2 AlN_(x) 21 nm/ZnSnO_(x) 5nm/ZAO 8 nm/Ag 9 nm/ ZAO 3.8 nm/ZnSnO_(x) 37 nm/AlN_(x) 17.5nm/NiSi₂N_(x) 9 nm/AlN_(x) 17.5 nm/ZAO 6.3 nm/Ag 16 nm/ZAO 3.8nm/AlN_(x) 21 nm/ ZnSnO_(x) 10 nm Example 18 −3.52 −4.28 20.36 2.48 6.710.44 −0.55 9.8 −1.32 0.37 58.45 60.03 1 AlN_(x) 21 nm/ZnSnO_(x) 5 nm/ZAO8 nm/Ag 9 nm/ ZAO 3.8 nm/ZnSnO_(x) 37 nm/AlN_(x) 27.5 nm/NiSi₂N_(x) 9.0nm/AlN_(x) 7.5 nm/ZAO 6.3 nm/Ag 16 nm/ZAO 3.8 nm/AlN_(x) 21 nm/ZnSnO_(x) 10 nm Example 19 (Comparative) −6.75 −7.78 18.34 1.99 14.491.9 −19 13.22 −0.84 −5.96 55.74 58.36 5+ AlN_(x) 21 nm/ZnSnO_(x) 5nm/ZAO 8 nm/Ag 9 nm/ ZAO 3.8 nm/ZnSnO_(x) 37 nm/AlN_(x) 35 nm/ZAO 6.3nm/Ag 16 nm/NiSi2 4 nm/ ZAO 3.8 nm/AlN_(x) 21 nm/ ZnSnO_(x) 10 nmExample 20 (Comparative) −4.77 2.21 8.32 3.8 4.67 2.94 −23.34 11.65 3.08−21 56.7 60.78 4/5 AlN_(x) 21 nm/ZnSnO_(x) 5 nm/ZAO 8 nm/Ag 9 nm/ ZAO3.8 nm/ZnSnO_(x) 37 nm/AlN_(x) 35 nm/ZAO 6.3 nm/Ag 16 nm/ZAO 3.8nm/NiSi₂ 4 nm/ZAO 3.8 nm/AlN_(x) 21 nm/ZnSnO_(x) 10 nm Example 21 −1.452.39 10.57 −1.2 −5.62 0.08 −1.37 9.21 −0.93 0.12 57.23 87.21 1 Singlelayer of Fe/Si 40:60 atomic ratio 3.9 nm Example 22 −1.34 0.93 8.55−0.38 −1.49 −0.73 −1.25 7.34 −0.32 −0.72 54.7 85.21 0 Single layer ofFe/Si 20:80 atomic ratio 3.7 nm Example 23 −1.22 4.1 9.69 −0.99 −4.480.05 0.32 8.79 −0.74 −0.85 50.77 84.87 0 Single layer of Fe/Si 50:50atomic ratio 4.2 nm Example 24 −1.13 −3.26 18.92 −0.59 8.4 −2.87 1.3217.68 −2.62 1.44 58.18 59.45 0 AlN_(x) 35 nm/Fe/Si 40:60 atomic ratio3.9 nm/AlN_(x) 35 nm Example 25 −0.88 −2.31 20.61 −0.87 2.27 −2.25 −3.8815.43 −2.17 −2.72 53.94 52.9 1 AlN_(x) 35 nm/Fe/Si 60:40 atomic ratio3.5 nm/AlN_(x) 35 nm Example 26 −0.16 3.3 27.41 −1.76 −0.31 −2.74 −0.9323.69 −2.94 −1.83 53.16 56.9 0 AlN_(x) 35 nm/Fe/Si 20:80 atomic ratio3.7 nm/AlN_(x) 35 nm Example 27 −0.97 −3.26 19.08 −0.91 3.37 −2.74 −0.7115.8 −2.6 −1.77 54.69 56.26 2 AlN_(x) 35 nm/Fe/Si 50:50 atomic ratio 4.2nm/AlN_(x) 35 nm Example 28 −0.94 −3.78 18.52 −0.53 7.13 −2.51 −0.7715.6 −2.55 0.12 54.27 53.13 2 AlN_(x) 35 nm/Fe/Si 70:30 atomic ratio 4.1nm/AlN_(x) 35 nm Example 29 −0.86 −3.85 18.55 −0.88 6.85 −2.73 −0.5715.97 −2.63 −0.18 55.44 55.9 2 AlN_(x) 35 nm/Fe/Si 55:45 atomic ratio4.0 nm/AlN_(x) 35 nm Where: AD = as deposited, HT = after heattreatment, Colour T = colour in transmission, Colour Rc = colour inreflection when viewed from the coated side of the pane, Colour Rg =colour in reflection when viewed from the non-coated (glass) side of thepane, and % T_(L) = percentage light transmittance. The methodology usedto collect the data in Table 1 is set out below. In Table 1, for eachexample the layers were deposited onto a glass pane in sequence startingwith the first layer shown.

Heat Treatability Tests

After the deposition of the coatings of Examples 1-29, TL and Colour Rgwere measured and the samples were heat treated at about 650° C. forabout 5 minutes. Thereafter haze, T_(L), Colour T, Colour Rc, and ColourRg were measured. The results are listed in Table 1 above.

The values stated for the % light transmittance % T_(L) of the coatedglass panes in the Examples 1-29 were derived from measurementsaccording to EN 140.

The colour characteristics were measured and reported using the wellestablished CIE LAB a*, b* coordinates (see e.g. [0030] and [0031] in WO2004-063 111 Al).

For relatively neutral colours it is generally preferred that each ofthe colour characteristics −15≤(a* or b*)≤15.

A subjective visible haze scoring system was applied to the Examples.The quality assessment system described hereinafter was found to beneeded to distinguish better the visual quality of coatings under brightlight conditions, properties that are not fully reflected by standardhaze values measured in accordance with ASTM D 1003-61.

The evaluation system considers the more macroscopic effect of visiblefaults in the coating which cause local colour variations where thecoating is damaged or imperfect (haze score in Table 1). Macroscopiceffects of visible faults in the coating after a heat treatment (allexamples exhibit no haze before a heat treatment) were assessedsubjectively by viewing samples under bright light. The evaluation isbased upon a perfectness scoring (rating) system using scores between 0(perfect, no faults) through to 3 (high number of clearly visible faultsand/or spots) up to 5 (dense haze, often already visible to the nakedeye), rating the visual appearance of the coated glass samples after aheat treatment.

The visual evaluation was carried out by using a 2.5 million candelapower beam (torch) that is directed at incidence angles between about−90° to about +90° (relative to normal incidence) in two orthogonalplanes (i.e. turning the torch first in a horizontal plane and then in avertical plane) onto a coated glass pane that is arranged in front of ablack box. The black box has a sufficiently large size such that severalcoated glass samples can be evaluated at the same time. The coated glasspanes are observed and their visual quality was assessed by varying theangle of incidence as described above, by directing the light beam fromthe observer through the coated glass panes. The coated glass panes werearranged in front of the black box such that their coating faced theobserver. Heat treated coated glass panes with any score ≥3 areconsidered as having failed the test.

Summary of Results

Comparative examples 1 and 2 are panes coated with stacks that do notcontain an absorbing layer as required by the present invention.Therefore these two comparative examples exhibit much higher lighttransmittance than the other examples.

Examples 3 and 4 are panes coated with stacks that contain a layer ofFe₂Si₃ embedded between AlN_(x) layers in a central anti-reflectionlayer. Only a thin layer of Fe₂Si₃ is required to achieve high visiblelight absorption. The haze is acceptable and the colour characteristicsare relatively neutral.

Example 5 is a pane coated with a stack that contains a layer of Fe₂Si₃contacting an AlN_(x) layer in a central anti-reflection layer. Again,only a thin layer of Fe₂Si₃ is required to achieve high visible lightabsorption. The haze is acceptable and the colour characteristics arerelatively neutral.

Examples 6 and 8 are panes coated with stacks that contain a layer ofFe₂Si₃N_(x) embedded between AlN_(x) layers in a central anti-reflectionlayer and an upper anti-reflection layer respectively. A thicker layerof Fe₂Si₃N_(x) is necessary to achieve comparable visible lightabsorption to that achieved with the use of a layer of Fe₂Si₃. The hazeis acceptable. Some of the colour values for example 8 are not ideal interms of neutrality.

Example 7 is a pane coated with a stack that contains a layer of Fe₂Si₃embedded between AlN_(x) layers in an upper anti-reflection layer.Again, only a thin layer of Fe₂Si₃ is required to achieve high visiblelight absorption. The haze is acceptable and the colour characteristicsare generally relatively neutral.

Comparative Example 9 is a pane coated with a stack that contains alayer of NiSi₂ located between layers of Ag and ZAO in a centralanti-reflection layer. This example exhibits unacceptable haze.

Comparative Example 10 is a pane coated with a stack that contains alayer of NiSi₂ located between layers of AlN_(x) and ZAO in a centralanti-reflection layer. This example also exhibits unacceptable haze.

Examples 11-16 are panes coated with stacks that contain a layer ofNiSi₂ embedded between AlN_(x) layers in a central anti-reflectionlayer. Examples 11 and 12 use different thicknesses of the NiSi₂ layerand each of examples 13-16 embeds the layer of NiSi₂ between two AlN_(x)layers that have a different thickness from each other. The haze isacceptable and the colour characteristics are relatively neutral in allcases. These examples show that the thicknesses of the AlN_(x) layersare not crucial for functionality.

Examples 17 and 18 are panes coated with stacks that contain a layer ofNiSi₂N_(x) embedded between AlN_(x) layers in a central anti-reflectionlayer. Example 18 embeds the layer of NiSi₂N_(x) between two AlN_(x)layers that have a different thickness from each other. A thicker layerof NiSi₂N_(x) is necessary to achieve comparable visible lightabsorption to that achieved with the use of a layer of NiSi₂. The hazeis acceptable and the colour values are generally acceptable in terms ofrelative neutrality.

Comparative Examples 19 and 20 are panes coated with stacks that containa layer of NiSi₂ located in an upper anti-reflection layer. InComparative Example 19 the layer of NiSi₂ is located between layers ofAg and ZAO, and in Comparative Example 20 the layer of NiSi₂ is embeddedbetween layers of ZAO. Both of these Comparative Examples exhibitunacceptable haze.

Examples 21-23 are panes coated with single layers of Fe/Si of varyingatomic ratios. These coated panes exhibit high light absorption beforeheat treatment and excellent haze. These coated panes also exhibitessentially neutral colours which demonstrates that these Fe/Si layerswould not per se adversely affect the colour neutrality of a multilayercoated pane.

Examples 24-29 are panes coated with single layers of Fe/Si of varyingatomic ratios embedded between AlN_(x) layers. These coated panesexhibit high light absorption, acceptable haze characteristics andgenerally essentially neutral colours.

It is worth noting that the thicknesses of the layers in the stacks ofExamples 3-20 have not been optimised for inclusion of the absorbinglayer, i.e. more neutral colour values could be obtained by altering thedielectric layer thicknesses.

The invention is not restricted to the details of the foregoingembodiments. The invention extends to any novel one, or any novelcombination, of the features disclosed in this specification (includingany accompanying claims, abstract and drawings), or to any novel one, orany novel combination, of the steps of any method or process sodisclosed.

1. A heat treated coated glass pane comprising at least the followinglayers: a glass substrate; and a lower anti-reflection layer; whereinthe lower anti-reflection layer comprises in sequence from the glasssubstrate; a base layer based on an (oxi)nitride of Silicon and/or an(oxi)nitride of Aluminium and/or alloys thereof; and/or an oxide ofTitantium; and/or an oxide of Zirconium located directly on the glasssubstrate; a layer based on an oxide of Zinc and Tin and/or an oxide ofTin; and a top layer based on an oxide of Zinc; a silver-basedfunctional layer; located directly on the top layer based on an oxide ofZinc; and a further anti-reflection layer located above the silver-basedfunctional layer and comprising: a barrier layer located directly on thesilver-based functional layer; and at least one absorbing layer based onat least one nickel silicide and/or nickel silicide nitride; and atleast one layer based on an (oxi)nitride of Si and/or an (oxi)nitride ofAl and/or alloys thereof, and wherein the at least one absorbing layercontacts directly the at least one layer based on an (oxi)nitride of Siand/or an (oxi)nitride of Al and/or alloys thereof; and wherein afterheat treatment the coated glass pane comprises neutral colorcharacteristics according to CIE LAB a*, b* coordinates such that−15≤(a* or b*)≤15.
 2. The coated glass pane according to claim 1,wherein the at least one absorbing layer is embedded between andcontacts two layers based on an (oxi)nitride of Si and/or an(oxi)nitride of Al and/or alloys thereof.
 3. The coated glass paneaccording to claim 1, wherein the at least one absorbing layer contactsdirectly at least one layer based on a nitride of Al.
 4. The coatedglass pane according to claim 1, wherein the at least one absorbinglayer is embedded between and contacts directly two layers based on anitride of Al.
 5. The coated glass pane according to claim 1, whereinthe pane comprises more than one silver-based functional layer andwherein each silver-based functional layer is spaced apart from anadjacent silver-based functional layer by a central anti-reflectionlayer.
 6. The coated glass pane according to claim 1, wherein the atleast one absorbing layer is located in the further anti-reflectionlayer.
 7. The coated glass pane according to claim 5, wherein the atleast one absorbing layer is located in the central anti-reflectionlayer.
 8. The coated glass pane according to claim 1, wherein the atleast one absorbing layer has a thickness in the range of 0.5 nm to 12nm.
 9. The coated glass pane according to claim 1, wherein the at leastone absorbing layer has a thickness in the range of 1 nm to 10 nm. 10.The coated glass pane according to claim 1, wherein the layer(s) basedon an (oxi)nitride of Si and/or an (oxi)nitride of Al and/or alloysthereof each independently have a thickness of at least 5 nm but at most25 nm.
 11. A multiple glazing incorporating a coated glass pane inaccordance with claim 1.